Pierre Janet’s L'Automatisme psychologique, originally published in 1889, is one of the earliest and most important books written on the study of trauma and dissociation. Here it is made available, in two volumes, in English for the first time, with a new preface by Giuseppe Craparo and Onno van der Hart. Catalepsy, Memory, and Suggestion in Psychological Automatism, the first volume, examines three aspects of trauma and dissociation. Janet first explores catalepsy and analogous states, including comparing catalepsy to somnambulism, then discusses somnambulism, memory, and forgetting. Finally, Janet considers suggestion, amnesia, and distraction, as well as considering characteristics of suggestible individuals. Janet’s work is an unsurpassed experimental study of human actions in their simplest and most rudimentary forms, and a fundamental contribution to our understanding of trauma-related dissociation. This seminal work will be of great interest to researchers and students of psychoanalysis, philosophy, and modernism, as well as psychotherapists and psychoanalysts working with clients who have experienced trauma. It is accompanied by Subconscious Acts, Anesthesias, and Psychological Disaggregation in Psychological Automatism: Partial Automatism.